1. Field of the Invention
The present invention relates to a process and apparatus for carrying out reactions of the type in which particulate solids, for example, fluidizable particulate catalysts, are used to facilitate a reaction during which the particles are degraded and require regeneration. In such processes the solids are typically circulated between a reaction zone and a regeneration zone. More specifically, the present invention relates to a process and apparatus in which the temperature of the recirculated regenerated solids may be adjusted.
2. Related Art
U.S. Pat. No. 4,668,802 (R. M. Contractor) discloses a process for vapor phase catalytic oxidation of butane to maleic anhydride and various by-products over a vanadium-phosphorus oxide catalyst. As illustrated in FIGS. 1-3, and described in corresponding portions of the Patent, use of recirculating particulate solid catalysts is disclosed, including the embodiments of FIGS. 1 and 2 in which the regeneration zone is comprised of two parts, a riser section and fluid bed section.
U.S. Pat. No. 2,589,124 (J. W. Packie) discloses a method and apparatus for handling fluidized solids in the catalytic cracking of hydrocarbons. The Patent discloses circulating fluidized catalyst particles between the reactor and regeneration vessels by standpipes and transfer lines which serve as manometer-like seals while serving to circulate the fluidized catalyst between the regenerator 14 and the reactor 10, each of which contains a fluidized bed of the solid particulate catalyst. Spent catalyst withdrawn from reactor 10 is flowed downwardly through a stripper 17 which is provided with a plurality of baffles 18. Steam or other stripping gas is introduced through line 19, as explained at column 6, lines 5-12. As is well-known in the art, by occluding a portion of the vessel cross-sectional area, the baffles 18 serve to limit vertical mixing of the fluidized particles in order to enhance efficiency of the stripping operation, which is designed to remove reaction products adhering to the catalyst particles.
U.S. Pat. No. 4,388,218 (F. Rowe) discloses a process and apparatus for the regeneration of catalytic cracking catalyst particles. As illustrated in the sole Figure of the Patent, the spent catalyst particles are stripped by steam supplied through inlet 12 in a stripping section in which the chevron-shaped markings apparently indicate the presence of baffles. A pair of fluidized bed vessels, one mounted vertically above the other with separate and distinct vapor phases and with a transfer conduit therebetween (column 5, line 31 et seq), is provided for regeneration of the catalyst. As described beginning at column 6, line 59, the catalyst particles, partially regenerated in the upper regeneration zone 14, are transferred by gravity into the lower regeneration zone 21 in which regeneration is completed by burning off accumulated coke on the catalyst particles. The exothermic heat of this burning reaction is used to raise the temperature of the catalyst particles to that required for cracking the oil feed supplied to the oil reactor 1. An optional series of cooling coils 25 within zone 21 (see column 5, line 66 to column 6, line 8) is used to absorb surplus heat, if any, as described at column 7, lines 1-6, prior to recirculating the regenerated catalyst.
U.S. Pat. No. 3,563,911 (R. W. Pfeiffer et al) and U.S. Pat. No. 3,661,800 (R. W. Pfeiffer et al) both show staged fluidized catalyst regeneration processes. Patent No. 3,563,911 shows a fluidized bed of catalyst in a regenerator divided into two side-by-side sections, numbered 4 and 6 in FIG. 1, by an arched baffle 3 which is provided with weirs 8. Patent No. 3,661,800 shows a staged regenerator in which the two portions of the bed of regenerated catalyst are divided by a baffle means into two sections, one above the other. Specifically, FIG. 2 of Patent No. 3,661,800 shows a reduced-diameter extension 102 of the regenerator vessel which includes a doughnut baffle 103 (and may include additional baffles, not shown) to ensure that no significant backmixing of catalyst occurs. See column 8, lines 58-75.